A method to prepare suspension cultures of highly viable pinealocytes is described. Pineal glands of neonatal or adult rats can be used; the best yield is obtained from neonatal glands. Morphological examination of the cells indicates that they have a normal, healthy appearance and retain some structures typical of neonatal pinealocytes. During the first 24 h of culture, the cells aggregate into small clusters; after several days, larger aggregates can be seen. Biochemical studies indicate that adrenergic stimulation of these cells causes a 30 to 100-fold increase in serotonin iV-acetyltransferase activity, a response which is unique to the pineal gland. The relative order of potency of several adrenergic agonists is l-isoproterenol > l-norepinephrine ≥ lepinephrine > phenylephrine. Serotonin, tyramine, histamine, carbachol, y-aminobutyric acid, cocaine, and desmethylimipramine are inactive. Studies using adrenergic and metabolic inhibitors indicate that the regulation of N-acetyltransferase in these cells has the same characteristics of that seen in adult tissue. In addition, these cells synthesize protein and RNA from radioactive precursors, convert tryptophan to serotonin, and Nacetylate endogenous serotonin.

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